Method of forming a MOS transistor with improved threshold voltage stability

摘要

The gate for at least one transistor is formed on the surface of the semiconductor substrate and the gate is utilized as a mask to form a lightly doped drain of the transistor. A low thermal budget deposition process is performed to form a silicon nitride layer on the surface or the semiconductor substrate. An ion implantation process is performed to implant fluorine atoms into the silicon nitride layer. After that, an etching process is performed to form a spacer in the periphery of the gate. Finally, a source/drain of the transistor is formed. The implanted fluorine atoms bond with the hydrogen atoms and keep them from becoming interface trapped charges. This increases the threshold voltage stability of the transistor.